Maximus IX Hero and slow Samsung EVO 970 SSD

I've got Maximus IX Hero and Samsung EVO 970 SSD 500GB. I've got some problem with Windows 10 last week. So I was checking it with OS booted from USB stick. And I started to check my SSD speeds. I repaired Windows. But I think my OS SSD is very slow. I don't know if this is new problem or it was always like that.

I've put Samsung EVO 970 in first, then in second slot on motherboard, and there is no significant change in speed. In Samsung Magician I've got 650-680 MB/s of sequential write speed.

In CystalDiskMark I've got better results.

But aren't those speeds too slow?

I installed NVMe Samsung driver. What else can I do?

Last edited by buzka; 11-20-2019 at 10:26 PM.
Reason: addeed system information